Metal oxide precursor, preparation method therefor, and use thereof

Abstract

A metal oxide precursor, a preparation method therefor, and a use thereof. The metal oxide precursor comprises dispersed single crystal particles and agglomerate particles partially formed by the single crystal particles; the dispersion degree K of the metal oxide precursor is 0.467 to 0.917, and K=D50 / (η×D90), wherein D50 is the corresponding particle size when the cumulative particle size distribution percentage of the metal oxide precursor reaches 50%, D90 is the corresponding particle size when the cumulative particle size distribution percentage of the metal oxide precursor reaches 90%, η is the volume deviation coefficient, and η is equal to 0.6.

Description

Metal oxide precursor and preparation method and application thereof

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311871680X and invention name “Metal oxide precursors, preparation methods and applications thereof”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a metal oxide precursor and a preparation method and application thereof. Background Art

[0003] The statements here only provide background information related to the present application and do not necessarily constitute prior art. The metal oxide precursors prepared by the traditional spray pyrolysis method usually have serious agglomeration phenomenon, which leads to a low specific surface area of ​​the metal oxide precursor, resulting in low sintering activity, increased energy consumption and high production cost during the sintering of the positive electrode material. Therefore, the agglomeration phenomenon of the metal oxide precursors prepared by the traditional spray pyrolysis method is usually improved by adding surfactants, or grinding and crushing the metal oxide precursors. However, these methods not only increase costs and reduce production efficiency, but also affect the performance test stability of the positive electrode material. Therefore, it is necessary to provide a highly dispersible metal oxide precursor that can be directly used to prepare positive electrode materials without the need for grinding, crushing and other treatments.

[0004] Application Contents

[0005] One of the purposes of the embodiments of the present application is to provide a metal oxide precursor and a preparation method and application thereof, aiming to provide a highly dispersed metal oxide precursor that can be directly used to prepare positive electrode materials without the need for grinding, crushing, or other treatments.

[0006] The technical solution adopted in the embodiment of this application is:

[0007] In a first aspect, a metal oxide precursor is provided, wherein the metal oxide precursor comprises dispersed single crystal particles and agglomerated particles partially formed by the single crystal particles;

[0008] The dispersion degree K of the metal oxide precursor is 0.467 to 0.917, and K=D 50 / (η×D 90 ), where D 50 is the particle size corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor reaches 50%, D 90 is the particle size corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor reaches 90%, and η is the volume deviation coefficient, η=0.6.

[0009] In one embodiment, 1.5 μm ≤ D 50 ≤4.0μm.

[0010] In one embodiment, 4 μm ≤ D 90 ≤10μm.

[0011] In one embodiment, the dispersion degree K of the metal oxide precursor is 0.5 to 0.9.

[0012] In one embodiment, the dispersion degree K of the metal oxide precursor is 0.6 to 0.8.

[0013] In one embodiment, the specific surface area of ​​the metal oxide precursor is 4 m 2 / g to 12m 2 / g.

[0014] In one embodiment, the bulk density of the metal oxide precursor is 0.4 g / cm 3 to 1.2g / cm 3 .

[0015] In one embodiment, the tap density of the metal oxide precursor is 1.0 g / cm 3 Up to 2.5g / cm 3 .

[0016] In one embodiment, the equivalent diameter of the agglomerate particles is 5 to 30 times the particle size of the single crystal particles.

[0017] In one embodiment, in the metal oxide precursor, the dispersion degree of a single agglomerate particle is K=S2 / nS1, wherein S1 is the surface area of ​​a single single crystal particle in the agglomerate particle, n is the number of single crystal particles in the agglomerate particle, and S2 is the surface area of ​​the agglomerate particle.

[0018] In one embodiment, the metal oxide precursor has a general chemical formula of Mn a M 1-a O2, wherein 0.1≤a≤0.9, and M is selected from at least one of Ni, Fe, Cu, Zn, Co, Mg, Al, and Ti.

[0019] In one embodiment, the metal content of the metal oxide precursor is greater than or equal to 70%.

[0020] In a second aspect, the present application provides a method for preparing a metal oxide precursor, wherein the preparation method is selected from a spray pyrolysis method.

[0021] In one embodiment, the pyrolysis temperature of the spray pyrolysis method is 500°C to 1000°C.

[0022] In one embodiment, the frequency of the feeding device of the spray pyrolysis method is 25 Hz to 45 Hz.

[0023] In one embodiment, the flow rate of the feeding device of the spray pyrolysis method is 0.3 m³ / h to 0.7 m³ / h.

[0024] In a third aspect, the present application provides a positive electrode material made from the above-mentioned metal oxide precursor or the metal oxide precursor prepared by the above-mentioned method.

[0025] Fourthly, the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer arranged on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the above-mentioned positive electrode material.

[0026] In a fifth aspect, the present application provides a secondary battery comprising the above-mentioned positive electrode sheet.

[0027] The beneficial effect of the metal oxide precursor provided in the embodiment of the present application is that the degree of dispersion K of the metal oxide precursor is 0.467 to 0.917. Under this specific degree of dispersion, the metal oxide precursor effectively reduces the agglomeration phenomenon of the metal oxide precursor, and can be directly used to prepare the positive electrode material without the need for grinding, crushing and other treatments. Even if there are some agglomerate particles, since the metal oxide precursor has a certain degree of dispersion, the agglomerate particles are also very easy to disperse completely during the preparation of the positive electrode material. It is beneficial to improve the uniformity of the mixing effect, so that the obtained positive electrode material has good consistency, which is not only beneficial to improving the performance test stability of the positive electrode material, but also beneficial to reducing costs and improving production efficiency. On the other hand, the metal oxide precursor has a relatively high specific surface area, which is beneficial to improving the sintering activity of the positive electrode material, thereby reducing production energy consumption.

[0028] The beneficial effects of the method for preparing a metal oxide precursor provided in the embodiments of the present application include: it can be prepared by spray pyrolysis, resulting in a dispersion degree K of 0.467 to 0.917, effectively reducing the agglomeration of the metal oxide precursor, and can be directly used to prepare positive electrode materials without the need for grinding, crushing, or other processing. At the same time, the metal oxide precursor has a relatively high specific surface area, which is beneficial for improving the sintering activity of the positive electrode material, thereby reducing production energy consumption.

[0029] The beneficial effect of the positive electrode material provided in the embodiment of the present application is that when the metal oxide precursor of the embodiment of the present application is used to prepare the positive electrode material, it is easier to obtain a single crystal positive electrode material with good uniformity, which is beneficial to improving the discharge capacity and cycle performance of the positive electrode material.

[0030] The beneficial effect of the positive electrode sheet provided in the embodiment of the present application is that the positive electrode material layer of the positive electrode sheet in the embodiment of the present application includes the above-mentioned positive electrode material with discharge capacity and cycle performance, thereby improving the energy density, cycle stability and other electrochemical properties of the positive electrode sheet.

[0031] The beneficial effect of the secondary battery provided by the embodiment of the present application is that the embodiment of the present application applies a positive electrode sheet with high energy density, cycle stability and other characteristics to the secondary battery, which can improve the electrochemical properties of the secondary battery such as cycle stability and cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] FIG1 is a scanning electron microscope image of the metal oxide precursor prepared in Example 1 of the present application;

[0034] FIG2 is a scanning electron microscope image of the metal oxide precursor prepared in Example 2 of the present application;

[0035] FIG3 is a scanning electron microscope image of the metal oxide precursor prepared in Comparative Example 1 of the present application;

[0036] FIG4 is a scanning electron microscope image of the metal oxide precursor prepared in Comparative Example 2 of the present application. Modes for Carrying Out the Invention

[0037] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit this application.

[0038] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The terms "upper", "lower", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of description and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field belonging to the embodiment of the present application. The terms used herein in the specification of the embodiment of the present application are only for the purpose of describing specific implementation or embodiment, and are not intended to limit the embodiment of the present application. The optional range of the term "and / or" used herein includes any one of two or more relevant listed items, also includes any and all combinations of relevant listed items, and any and all combinations include any two relevant listed items, any more relevant listed items, or the combination of all relevant listed items.

[0040] In order to illustrate the technical solution of this application, the following is a detailed description with reference to specific drawings and embodiments.

[0041] Some embodiments of the present application provide a metal oxide precursor, the metal oxide precursor comprising dispersed single crystal particles and agglomerated particles partially formed from the single crystal particles;

[0042] The dispersion degree K of the metal oxide precursor is 0.467 to 0.917, and K=D 50 / (η×D 90 ), where D 50 D is the particle size corresponding to the cumulative particle size distribution percentage of the metal oxide precursor reaching 50%. 90 is the particle size corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor reaches 90%, η is the volume deviation coefficient, η=0.6.

[0043] It should be noted that, in theory, when there is no agglomeration, the metal oxide precursor has a maximum specific surface area; when local agglomeration occurs between particles, the closer the agglomerated particles are and the smaller the gaps are, the more serious the agglomeration is, resulting in a smaller specific surface area.

[0044] Based on this, the present invention defines the degree of dispersion K of a metal oxide precursor as the ratio of the actual specific surface area of ​​the agglomerates in the metal oxide precursor to the theoretical specific surface area of ​​the constituent particles of the agglomerates in a dispersed state. The degree of dispersion of a single agglomerate particle in a metal oxide precursor is K = S2 / nS1, where S1 is the surface area of ​​a single constituent particle (i.e., a single crystal particle) in the agglomerate, n is the number of constituent particles (i.e., single crystal particles) in the agglomerate, and S2 is the surface area of ​​the agglomerate particles.

[0045] Use D 50 The value represents the particle size corresponding to the dispersed particles, and D 90 The value represents the particle size corresponding to the agglomerated particles. Under the condition that the density of the same material remains unchanged, the mass of the same volume of material is equal, and then the volume ratio is deduced to obtain n=η×(D 90 ) 3 / (D 50 ) 3 , Among them, considering that the pores between the agglomerated particles will cause a certain deviation in volume, the volume deviation coefficient η is set to 0.6, and according to D 50 and D 90 Derived from S1 and S2, we get K=D 50 / (η×D 90 The volume deviation coefficient η is based on the assumption that the equivalent diameter of agglomerated particles is 5 to 30 times that of single crystal particles. The porosity is estimated from two-dimensional and three-dimensional perspectives, so the volume deviation coefficient η takes an average value of 0.6.

[0046] The degree of dispersion K of the metal oxide precursor in the embodiment of the present application is 0.467 to 0.917. When the degree of dispersion K is in the range of 0.467~0.917, the particles are well dispersed and there is less agglomeration. When K>0.467, it means that a considerable portion of the particles in the system are dispersed. As the K value increases, the proportion of dispersed particles increases and the proportion of agglomerates decreases. Within this range, the interaction force between the particles decreases, and the particles are more inclined to remain in a dispersed state. The higher the degree of dispersion K, the more the particles can fully expose their surface area, so the surface area contribution of a single particle is greater. When K is 0.917, almost all particles are in a dispersed state, the effective surface area participating in the electrochemical reaction increases, and the electrochemical reaction activity of the material is the highest. The degree of dispersion K of the metal oxide precursor is 0.467 to 0.917. At this specific degree of dispersion, on the one hand, the agglomeration phenomenon of the metal oxide precursor is effectively reduced, and it can be directly used to prepare positive electrode materials without the need for grinding, crushing, and other treatments. Even if some aggregated particles are present, the metal oxide precursor's relatively high degree of dispersion allows for complete dispersion during the cathode material preparation process. This improves the uniformity of the mixing process, resulting in a more consistent cathode material. This not only enhances the stability of cathode material performance testing but also helps reduce costs and increase production efficiency. Furthermore, the metal oxide precursor's relatively high specific surface area enhances the cathode material's sintering activity, thereby reducing production energy consumption.

[0047] In one embodiment, the particle size corresponding to the cumulative particle size distribution percentage of the metal oxide precursor reaching 50% may be 1.5 μm to 4.0 μm, that is, 1.5 μm ≤ D 50 ≤4.0μm. For example, the particle size corresponding to the cumulative particle size distribution percentage of the metal oxide precursor reaching 50% can be 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, etc., which are typical but non-limiting points or interval values ​​between any two points. 50 In this case, use D 50 To express the average particle size of single crystal particles, when D 50 The smaller the particle, the greater the surface energy of the particles. The particles tend to agglomerate to reduce the surface energy. Agglomeration will reduce the specific surface area, and then D 50 The smaller it is, the worse the dispersion is, that is, K is closer to 0. 50 The preferred size is 1.5 μm to 4.0 μm because: if the particle size is too small, the surface energy is high and it is easy to cause agglomeration, and the smaller the grain, the higher the proportion of grain boundaries, which may lead to more grain boundary defects and thus structural stability; if the particle size is too large, the diffusion path of lithium ions will become longer, thereby affecting the battery's rate capability, and if the particles are too large, it may make it difficult for the electrochemical reaction to proceed uniformly.

[0048] In one embodiment, the particle size corresponding to the cumulative particle size distribution percentage of the metal oxide precursor reaching 90% may be 4 μm to 10 μm, that is, 4 μm ≤ D 90 ≤10μm. For example, the particle size corresponding to the cumulative particle size distribution percentage of the metal oxide precursor reaching 90% can be 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc., which are typical but non-limiting points or interval values ​​between any two points. 90 In this case, use D 90 To express the equivalent diameter of the aggregate, when D 90 The larger the value, the more serious the agglomeration phenomenon, the smaller the specific surface area, and the worse the dispersion. 50 With D 90 There is a correlation between size, D 50 The larger the particle, the greater the relative D 90 The larger the D 90 Close to D 50 When , it means the degree of agglomeration is lighter, that is, the degree of dispersion is higher. 90 The preferred range is 4μm~10μm, which is consistent with D 50 The selected value of D 50 Cannot be too small, so the lower limit is 4μm, D 90 Too large indicates serious agglomeration, resulting in uneven particle size and distribution, affecting the electrochemical performance.

[0049] In the embodiment of the present application, the D of the metal oxide precursor is adjusted. 50 and D 90 , which helps ensure that the metal oxide precursor can meet the provided dispersion level K=D 50 / (η×D 90 ), and the dispersion degree K of the metal oxide precursor reaches 0.467 to 0.917. For example, the dispersion degree K of the metal oxide precursor can be any typical but non-limiting point value such as 0.467, 0.5, 0.6, 0.7, 0.8, 0.9, 0.917, or an interval value between any two point values.

[0050] In some embodiments, the dispersion degree K of the metal oxide precursor is 0.5 to 0.9. In other embodiments, the dispersion degree K of the metal oxide precursor is 0.6 to 0.8. In the above embodiments of the present application, the dispersion degree K of the metal oxide precursor can better facilitate the complete dispersion of the metal oxide precursor during the preparation of the positive electrode material, thereby improving the performance test stability of the positive electrode material, reducing costs, and improving production efficiency.

[0051] In one embodiment, the specific surface area of ​​the metal oxide precursor is 4 m 2 / g to 12m 2 / g; Exemplarily, the specific surface area of ​​the metal oxide precursor can be 4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g and other typical but non-limiting arbitrary point values ​​or interval values ​​between any two point values. The dispersion degree K of the metal oxide precursor in the embodiment of the present application is 0.467 to 0.917, so that the metal oxide precursor has a higher specific surface area. The relationship between the dispersion degree value K and the specific surface area S can be expressed as , where S1 is the surface area corresponding to a single particle, and S2 is the surface area corresponding to a single agglomerate. The more serious the agglomeration, the smaller the specific surface area, and the closer the K value is to 0. The closer the K value is to 1, the better the dispersion of the particles. When K=1, it indicates complete dispersion.

[0052] In one embodiment, the bulk density of the metal oxide precursor is 0.4 g / cm 3 to 1.2g / cm 3 For example, the bulk density of the metal oxide precursor can be 0.4 g / cm 3 , 0.5g / cm 3 , 0.6g / cm 3 , 0.7g / cm 3 , 0.8g / cm 3 , 0.9g / cm 3 , 1.0g / cm 3 , 1.1g / cm 3 , 1.2g / cm 3 Typical but non-restrictive arbitrary point values ​​or interval values ​​between any two point values. The degree of dispersion K of the metal oxide precursor in the embodiment of the present application is 0.467 to 0.917, so that the metal oxide precursor has a higher bulk density. If the degree of dispersion is too low, the particles are severely and irregularly agglomerated, affecting the stacking behavior of the particles. Although the agglomerates are tight inside, the gaps between the agglomerates are large, resulting in a low bulk density. If the degree of dispersion is too high, there are more gaps between the dispersed particles, resulting in a decrease in the compactness of the overall stacking. The degree of dispersion K of the present application is between 0.467 and 0.917, and it contains a small amount of agglomerates and dispersed particles at the same time. Small particles are filled in large pores to improve the bulk density. In this interval, the bulk density first increases and then decreases with the increase of K.

[0053] In one embodiment, the tap density of the metal oxide precursor is 1.0 g / cm 3 Up to 2.5g / cm 3 For example, the tap density of the metal oxide precursor may be 1.0 g / cm 3 , 1.2g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 , 1.8g / cm 3 , 2.0g / cm 3 , 2.2g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 Typical but non-limiting arbitrary point values ​​or interval values ​​between any two point values. The dispersion degree K of the metal oxide precursor in the embodiment of the present application is 0.467 to 0.917, which makes the metal oxide precursor have a higher tap density. Consistent with the relationship between K and bulk density described above, within the range of the dispersion degree K of 0.467 to 0.917, the tap density first increases and then decreases with the increase of K.

[0054] In the embodiment of the present application, the metal oxide precursor satisfies the dispersion degree K=D 50 / (η×D 90 ) based on a high degree of dispersion, containing both agglomerated and dispersed particles, which helps fill voids and thereby improves tap and compaction density. This allows for easier dispersion of metal oxide precursors during the preparation of positive electrode materials, facilitating uniformity in positive electrode coating, thereby improving the stability of positive electrode material performance testing, and contributing to cost reduction and improved production efficiency.

[0055] In one embodiment, the equivalent diameter of the agglomerate particles is 5 to 30 times the particle size of the single crystal particles. Exemplarily, the equivalent diameter of the agglomerate particles is 5 times, 6 times, 8 times, 10 times, 15 times, 20 times, 25 times, 30 times, or any other typical but non-restrictive point value or interval value between any two point values ​​of the single crystal particle size. In this case, if the agglomerate is too large, the electrochemical reaction is uneven, and the diffusion path of the lithium ions is long, affecting the rate capability. If the particle dispersion is too high, it is not conducive to improving the bulk density and tap density, resulting in a decrease in the capacity and energy density of the battery.

[0056] In the embodiment of the present application, the metal oxide precursor satisfies the dispersion degree K=D 50 / (η×D 90), by regulating the agglomeration size of single crystal particles in the agglomerate, D90 and D50 are made close, which is beneficial to the uniformity of positive electrode coating, so that the metal oxide precursor can be directly used to prepare positive electrode materials without grinding, crushing and other treatments.

[0057] In one embodiment, the metal oxide precursor has the general chemical formula Mn a M 1-a O2, wherein 0.1≤a≤0.9, and M is selected from at least one of Ni, Fe, Cu, Zn, Co, Mg, Al, and Ti. It is understood that the metal oxide precursor in the embodiment of the present application can be a binary metal oxide, a ternary metal oxide, or a quaternary metal oxide, which is not limited in the embodiment of the present application.

[0058] In one embodiment, the metal content of the metal oxide precursor is greater than or equal to 70%. This not only increases packaging capacity, thereby reducing transportation costs, but also increases the amount of packaging when used to prepare sodium-ion battery cathode materials, thereby facilitating increased production capacity and reduced energy consumption. For example, the metal content of the metal oxide precursor can be any typical but non-limiting value such as 70%, 75%, 80%, 85%, 90%, or 95%, or an interval between any two values.

[0059] The embodiment of the present application provides a method for preparing the above metal oxide precursor, and the preparation method is selected from the spray pyrolysis method.

[0060] The metal oxide precursors described in the embodiments of the present application can be produced by spray pyrolysis, resulting in a dispersion degree K of 0.467 to 0.917. This effectively reduces agglomeration of the metal oxide precursors, allowing them to be directly used to prepare cathode materials without the need for grinding or crushing. This also results in a relatively high specific surface area, which helps improve the sintering activity of the cathode material and thus reduces production energy consumption.

[0061] It should be noted that the specific operation of the spray pyrolysis method can refer to the existing method, and the embodiments of the present application will not be described in detail.

[0062] In one embodiment, the pyrolysis temperature of the spray pyrolysis method is 500°C to 1000°C. Exemplarily, the pyrolysis temperature of the spray pyrolysis method can be any typical but non-limiting value such as 500°C, 600°C, 700°C, 800°C, or 900°C, or an interval between any two values. Under these pyrolysis temperature conditions, lower pyrolysis temperatures result in poor particle crystallinity, uneven particle formation, smaller particle size, irregular morphology, increased agglomeration, and poor dispersibility. Higher pyrolysis temperatures result in better particle crystallinity, larger particle size, regular morphology, more uniform distribution, and improved dispersibility.

[0063] In one embodiment, the frequency of the feed device of the spray pyrolysis method is 25 Hz to 45 Hz, and can be 35 Hz to 40 Hz. For example, the frequency of the feed device of the spray pyrolysis method can be any typical but non-limiting value such as 25 Hz, 30 Hz, 35 Hz, 40 Hz, or 45 Hz, or an interval between any two values. Under these feeding frequency conditions, a low feeding frequency can fully decompose the droplets due to thermal heating, resulting in uniform particle size and good dispersion, which can reduce particle agglomeration. A high feeding frequency can unevenly heat the droplets, resulting in poor particle dispersion, easily forming an uneven particle distribution, easily agglomerating, and poor dispersion.

[0064] In one embodiment, the flow rate of the feed device of the spray pyrolysis method is 0.3m³ / h to 0.7m³ / h, and can be 0.35m³ / h to 0.55m³ / h. Exemplarily, the flow rate of the feed device of the spray pyrolysis method is 0.3m³ / h, 0.4m³ / h, 0.5m³ / h, 0.6m³ / h, 0.7m³ / h, and other typical but non-limiting arbitrary point values ​​or interval values ​​between any two point values. Under the flow rate conditions of the feed device, the feed flow rate is low: there are fewer atomized droplets, the thermal decomposition is more complete, the particle size is more uniform, the morphology is regular, the agglomeration phenomenon is less, and the degree of dispersion is better. The feed flow rate is high: there are more atomized droplets, the particle growth is prone to incomplete, resulting in uneven particles, increased agglomeration, and poor dispersion.

[0065] By regulating conditions such as pyrolysis temperature, feeding frequency and feeding flow rate, it is beneficial to improve the dispersion of the obtained metal oxide precursor and effectively improve the agglomeration phenomenon.

[0066] It should be noted that the pyrolysis temperature is the operating temperature of the pyrolysis device; if the frequency of the feeding device is 50Hz, which is equivalent to 100%, then when the frequency of the feeding device is 25Hz to 45Hz, 50% to 90% of 50Hz is used; when the frequency of the feeding device is 35Hz to 40Hz, 70% to 80% of 50Hz is used. The preparation method can meet the above-mentioned conditions such as pyrolysis temperature, feeding frequency, and feeding flow rate. It is understandable that other preparation methods that do not meet the above-mentioned conditions such as pyrolysis temperature, feeding frequency, and feeding flow rate can also make the metal oxide precursor meet the specific dispersion degree in the embodiments of this application under certain conditions, and the embodiments of this application do not limit this.

[0067] The embodiments of the present application also provide a positive electrode material prepared from the above metal oxide precursor.

[0068] When the metal oxide precursor of the embodiment of the present application is used to prepare the positive electrode material, it is easier to obtain a single crystal positive electrode material with good uniformity, which is beneficial to improving the discharge capacity and cycle performance of the positive electrode material.

[0069] It should be noted that the preparation method of the positive electrode material refers to the existing method, and the embodiments of this application will not be repeated here.

[0070] An embodiment of the present application further provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer disposed on the surface of the positive electrode current collector, wherein the positive electrode material layer comprises the above-mentioned positive electrode material.

[0071] The positive electrode material layer of the positive electrode sheet of the embodiment of the present application includes the above-mentioned positive electrode material with discharge capacity and cycle performance, thereby improving the electrochemical properties of the positive electrode sheet, such as energy density and cycle stability.

[0072] An embodiment of the present application further provides a secondary battery, comprising the above-mentioned positive electrode sheet.

[0073] The embodiments of the present application apply a positive electrode sheet having characteristics such as high energy density and cycle stability to a secondary battery, which can improve the electrochemical properties of the secondary battery, such as cycle stability and cycle life.

[0074] Exemplarily, the secondary battery may be a sodium ion battery.

[0075] In one embodiment, the positive electrode current collector may be a metal foil or a composite current collector, for example, aluminum foil is used as the metal foil; the composite current collector may be formed by forming a metal material on a polymer material substrate, wherein the metal material includes but is not limited to at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, and the polymer material substrate includes but is not limited to at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).

[0076] It can be understood that the positive electrode material layer also includes a binder and a conductive agent, wherein the binder can be any commercially available binder for positive electrode sheets, including but not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-fluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin, or a binder prepared by any known method, which is not limited to the examples of the present application; the conductive agent can be any commercially available conductive agent for sodium ion batteries, such as carbon black, graphite, etc.

[0077] The metal oxide precursors, their preparation methods, and applications are further described below through the following specific examples. However, those skilled in the art will appreciate that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the procedures were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used where the manufacturer is not specified are commercially available conventional products.

[0078] Example 1

[0079] Nickel salt, iron salt, and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 1:1:1. Then, under the conditions of a liquid inlet flow rate of 0.5 m³ / h and a feed frequency of 37.5 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 750°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NFM111.

[0080] The surface morphology of the metal oxide precursor prepared in this embodiment is shown in FIG1 . It can be seen that the metal oxide precursor contains single crystal particles and local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 17 to 24 times the particle size of the single crystal particles.

[0081] The metal oxide precursor D 50 2.58μm, D 90 The particle size is 5.98 μm and the apparent density (AD) is 0.67 g / cm 3 , tap density (TD) is 1.52g / cm 3 , the specific surface area (BET) is 4.43m 2 / g.

[0082] Through simulation calculation, it can be obtained that the metal oxide precursor prepared in this embodiment meets the dispersion degree K of 0.719.

[0083] Example 2

[0084] Iron salt and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 4:6. Then, under the conditions of a liquid inlet flow rate of 0.6 m³ / h and a feed frequency of 33.5 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 860°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula FM46.

[0085] The surface morphology of the metal oxide precursor prepared in this embodiment is shown in FIG2 . It can be seen that the metal oxide precursor contains single crystal particles and local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 12 to 18 times the particle size of the single crystal particles.

[0086] The metal oxide precursor D 50 1.98μm, D 90 The thickness is 4.25 μm and the apparent density (AD) is 0.74 g / cm 3 , the tap density (TD) is 1.84g / cm 3 , the specific surface area (BET) is 6.87m 2 / g.

[0087] Through simulation calculation, it can be obtained that the dispersion degree K of the metal oxide precursor prepared in this embodiment is 0.776.

[0088] Example 3

[0089] Nickel salt, copper salt, iron salt, and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 2:1:3:3. Then, under the conditions of a liquid inlet flow rate of 0.3 m³ / h and a feed frequency of 25 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 1000°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NCFM2133.

[0090] SEM testing shows that the metal oxide precursor contains single crystal particles and some local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 15 to 20 times the particle size of the single crystal particles.

[0091] The metal oxide precursor D 50 3.84μm, D 90 The particle size is 8.67 μm and the apparent density (AD) is 0.82 g / cm 3 , the tap density (TD) is 1.93g / cm 3 , the specific surface area (BET) is 9.69m 2 / g.

[0092] Through simulation calculation, it can be obtained that the dispersion degree K of the metal oxide precursor prepared in this embodiment is 0.738.

[0093] Example 4

[0094] Copper salt, iron salt and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 4:2:4. Then, under the conditions of a liquid inlet flow rate of 0.7 m³ / h and a feed frequency of 45 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 520°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is simply represented by CFM424.

[0095] SEM testing shows that the metal oxide precursor contains single crystal particles and some local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 24 to 30 times the particle size of the single crystal particles.

[0096] The metal oxide precursor D 50 1.56μm, D 90 The thickness is 4.21 μm and the apparent density (AD) is 0.46 g / cm 3 , tap density (TD) is 1.08g / cm 3 , the specific surface area (BET) is 4.39m 2 / g.

[0097] Through simulation calculation, it can be obtained that the dispersion degree K of the metal oxide precursor prepared in this embodiment is 0.618.

[0098] Example 5

[0099] Nickel salt, cobalt salt and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 6:1:3. Then, under the conditions of a liquid inlet flow rate of 0.7 m³ / h and a feed frequency of 40 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 610°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NCM613.

[0100] SEM testing shows that the metal oxide precursor contains single crystal particles and some local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 22 to 30 times the particle size of the single crystal particles.

[0101] The metal oxide precursor has a D50 of 2.15 μm, a D90 of 7.64 μm, and an apparent density (AD) of 0.47 g / cm 3 , tap density (TD) is 1.23g / cm 3 , the specific surface area (BET) is 4.98m 2 / g.

[0102] Through simulation calculation, it can be obtained that the dispersion degree K of the metal oxide precursor prepared in this embodiment is 0.915.

[0103] Example 6

[0104] Nickel salt, cobalt salt and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 6:1:3. Then, under the conditions of a liquid inlet flow rate of 0.3 m³ / h and a feed frequency of 25 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 920°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NCM613.

[0105] SEM testing shows that the metal oxide precursor contains single crystal particles and some local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 5 to 12 times the particle size of the single crystal particles.

[0106] The metal oxide precursor has a D50 of 3.98 μm, a D90 of 7.25 μm, and an apparent density (AD) of 0.46 g / cm 3 , the tap density (TD) is 1.13g / cm 3 , the specific surface area (BET) is 11.3m 2 / g.

[0107] Through simulation calculation, it can be obtained that the dispersion degree K of the metal oxide precursor prepared in this embodiment is 0.469.

[0108] Comparative Example 1

[0109] Nickel salt, iron salt, and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 1:1:1. Then, under the conditions of a liquid inlet flow rate of 0.75m³ / h and a feed frequency of 35Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 1050°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NFM111.

[0110] The surface morphology of the metal oxide precursor prepared in this embodiment is shown in FIG3 . It can be seen that the metal oxide precursor has serious agglomeration phenomenon, and the equivalent diameter of the agglomerates is about 28 to 45 times the particle size of the single crystal particles.

[0111] The metal oxide precursor D 50 4.6μm, D 90 The thickness is 17.32 μm and the apparent density (AD) is 0.35 g / cm 3, tap density (TD) is 0.94g / cm 3 , the specific surface area (BET) is 2.98m 2 / g.

[0112] Through simulation calculation, it can be found that the dispersion degree K of the metal oxide precursor prepared in this embodiment is only 0.443.

[0113] Comparative Example 2

[0114] Nickel salt, copper salt, iron salt, and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 2:1:3:3. The mixed metal salt solution is then introduced into a calcining furnace in the form of droplets at a liquid inlet flow rate of 0.28 m³ / h and a feed frequency of 23.5 Hz. Under a pyrolysis temperature of 480°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NCFM2133.

[0115] The surface morphology of the metal oxide precursor prepared in this embodiment is shown in FIG4 . It can be seen that the metal oxide precursor has serious agglomeration phenomenon, and the equivalent diameter of the agglomerates is about 35 to 50 times the particle size of the single crystal particles.

[0116] The metal oxide precursor D 50 0.85μm, D 90 The particle size is 3.15 μm and the apparent density (AD) is 0.36 g / cm 3 , tap density (TD) is 0.97g / cm 3 , the specific surface area (BET) is 3.38m 2 / g.

[0117] Through simulation calculation, it can be found that the dispersion degree K of the metal oxide precursor prepared in this embodiment is only 0.45.

[0118] Comparative Example 3

[0119] Nickel salt, iron salt, and manganese salt are prepared into a mixed metal salt solution in a metal atomic molar ratio of 1:1:1. Then, under the conditions of a liquid inlet flow rate of 0.75 m³ / h and a feed frequency of 40 Hz, the mixed metal salt solution is introduced into a roasting furnace in the form of droplets. Under the conditions of a pyrolysis temperature of 450°C, the droplets are subjected to processes such as evaporation, drying, thermal decomposition, and sintering to form a metal oxide precursor. The obtained metal oxide precursor product is represented by the simplified formula NFM111.

[0120] SEM testing shows that the metal oxide precursor contains single crystal particles and some local agglomerates formed by irregular agglomeration of single crystal particles. The equivalent diameter of the agglomerates is about 5 to 10 times the particle size of the single crystal particles.

[0121] The metal oxide precursor has a D50 of 1.8 μm, a D90 of 3.16 μm, and an apparent density (AD) of 0.41 g / cm 3 , tap density (TD) is 0.95g / cm 3 , the specific surface area (BET) is 6.9m 2 / g.

[0122] Through simulation calculation, it can be obtained that the dispersion degree K of the metal oxide precursor prepared in this embodiment is 0.95.

[0123] Application Examples

[0124] The metal oxide precursors prepared in Examples 1 to 6 and Comparative Examples 1 and 3 were mixed with sodium carbonate in a molar ratio of 1:1, and then placed in a muffle furnace. In an air atmosphere, the temperature was increased to 900°C at a heating rate of 5°C / min. After constant temperature sintering for 15 hours, the mixture was naturally cooled, crushed, and sieved to obtain a positive electrode material.

[0125] The prepared positive electrode material was made into a sodium ion button battery, and the capacity retention rate after 50 cycles was tested under the voltage condition of 2V-4.15V. The test results are shown in Table 1.

[0126] Table 1

[0127] Capacity retention rate after 50 cycles (%) Example 1 94.5 Example 2 91.6 Example 3 90.0 Example 4 92.5 Example 5 89.7 Example 6 88.5 Comparative Example 1 79.0 Comparative Example 2 72.0 Comparative Example 3 70.3

[0128] According to Table 1, the metal oxide precursors prepared in Examples 1 to 6 are used in the positive electrode materials of sodium ion batteries, which can enable the sodium ion batteries to achieve a capacity retention rate of more than 90% after 50 cycles under the voltage conditions of 2V-4.15V. Compared with Examples 1 to 6, in Comparative Example 1, due to the high liquid inlet flow rate and pyrolysis temperature, the thermal motion of the particles is enhanced, and the mutual collisions between the particles increase, thereby aggravating the agglomeration of the precursor particles and the degree of dispersion is lower than 0.467, resulting in poor performance stability; in Comparative Example 2, due to the low liquid inlet flow rate and pyrolysis temperature, the wet particles are more likely to adhere to each other in the initial stage to form larger particles, and the electrostatic force and van der Waals force between the particles will also cause agglomeration, making the degree of dispersion lower than 0.467, resulting in a performance stability of only about 72%. In Comparative Example 3, the K value is higher than 0.917, reaching 0.95, which also reduces the degree of dispersion, resulting in poor cycle stability.

[0129] The above are merely optional embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A metal oxide precursor, characterized in that, The metal oxide precursor includes single crystal particles in a dispersed state and agglomerated particles partially formed by the single crystal particles; The dispersion degree K of the metal oxide precursor is 0.467 to 0.917, and K = D 50 / (η×D 90 ), where D 50 is the particle size corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor reaches 50%, D 90 is the particle size corresponding to when the cumulative particle size distribution percentage of the metal oxide precursor reaches 90%, and η is the volume deviation coefficient, η = 0.

6.

2. The metal oxide precursor according to claim 1, wherein 1.5μm ≤ D 50 ≤ 4.0μm.

3. The metal oxide precursor according to claim 1, wherein, 4μm ≤ D 90 ≤ 10μm.

4. The metal oxide precursor according to any one of claims 1 to 3, characterized in that, The dispersion degree K of the metal oxide precursor is from 0.5 to 0.

9.

5. The metal oxide precursor according to claim 4, wherein The dispersion degree K of the metal oxide precursor is from 0.6 to 0.

8.

6. The metal oxide precursor according to claim 1, wherein The specific surface area of the metal oxide precursor is 4 m 2 / g to 12 m 2 / g.

7. The metal oxide precursor according to claim 1, wherein The loose bulk density of the metal oxide precursor is 0.4 g / cm 3 to 1.2 g / cm 3 .

8. The metal oxide precursor according to claim 1, wherein The tapped density of the metal oxide precursor is 1.0 g / cm 3 to 2.5 g / cm 3 .

9. The metal oxide precursor according to claim 1, wherein The equivalent diameter of the agglomerated particles is 5 to 30 times the particle size of the single crystal particles.

10. The metal oxide precursor according to claim 1, characterized in that, In the metal oxide precursor, the dispersion degree K of a single agglomerated particle = S2 / nS1, where S1 is the surface area of a single crystal particle in the agglomerated particle, n is the number of single crystal particles in the agglomerated particle, and S2 is the surface area of the agglomerated particle.

11. The metal oxide precursor according to claim 1, characterized in that, The chemical general formula of the metal oxide precursor is expressed as Mn a M 1-a O2, where 0.1 ≤ a ≤ 0.9, and M is selected from at least one of Ni, Fe, Cu, Zn, Co, Mg, and Al.

12. The metal oxide precursor according to claim 1, wherein The metal content of the metal oxide precursor is greater than or equal to 70%.

13. A method for preparing a metal oxide precursor according to any one of claims 1 to 12, characterized in that, The preparation method is selected from spray pyrolysis.

14. The method for preparing the metal oxide precursor according to claim 13, wherein The pyrolysis temperature of the spray pyrolysis is from 500°C to 1000°C.

15. The method for preparing a metal oxide precursor according to claim 13, wherein The frequency of the feeding device of the spray pyrolysis is from 25 Hz to 45 Hz.

16. The method for preparing a metal oxide precursor according to claim 13, wherein, The flow rate of the feeding device of the spray pyrolysis is from 0.3 m³ / h to 0.7 m³ / h.

17. A positive electrode material prepared from the metal oxide precursor according to any one of claims 1 to 12 or the metal oxide precursor prepared by the method according to any one of claims 13 to 16.

18. A positive electrode sheet, characterized in that, It includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, and the positive electrode material layer includes the positive electrode material according to claim 17.

19. A secondary battery, characterized in that, It includes the positive electrode sheet according to claim 18.

Images